libtorrent.org

libtorrent is released under the BSD license. You can use the library in your own project without releasing your source code; the only requirement is that you credit the author by including the libtorrent license in your software or documentation. Contributing improvements back to the project is appreciated but not required.

What the BSD license allows

The project's own description of its terms is short and permissive:

• Commercial and closed-source use is permitted. The site states explicitly that you can use the library in your project "without having to release its source code."
• No copyleft obligation. Unlike licenses that require derivative works to be open-sourced, the BSD terms here impose no such requirement.
• Modification is not restricted by the stated terms. The site does not attach conditions to modified versions beyond the credit requirement described below.

What your project must do

There is exactly one stated requirement: give credit to the author of the library by including the libtorrent license in your software or documentation.

In practice, that means placing the license text somewhere a user or reviewer can find it — for example:

• a LICENSES/ or third_party/ directory in your source tree,
• an open-source notices or credits screen in a desktop or mobile application,
• an acknowledgements section in your product documentation.

The site does not prescribe a specific location or format, so the choice of where to put the notice is yours; the condition is that the license is included and the author credited.

What is optional

The project says it is "greatly appreciated if additional features are contributed back to the open source project," and notes that patches can be emailed to the mailing list or posted to the bug tracker. This is a request, not a license condition — nothing in the stated terms obliges you to publish changes.

Practical checklist before shipping

1. Confirm you are using an official libtorrent release and keep a copy of the license text that shipped with it.
2. Add the license to your distribution — source tree, notices file, or in-product credits.
3. If you modify the library and want to share fixes, send a patch to the mailing list or file it on the bug tracker; if you prefer not to, no action is needed under the license.

Where to verify

The license statement appears on the libtorrent project site (libtorrent.org) alongside the introduction, which also describes the library as a feature-complete C++ BitTorrent implementation focused on CPU efficiency, memory efficiency, and ease of use. For the authoritative wording, read the license text distributed with the version you are using rather than relying on summaries.

libtorrent's official site lists bindings for Python, Java, golang, and node, and routes help through a mailing list and the #libtorrent IRC channel. Bugs go to the bug tracker or the GitHub page. The site also publishes troubleshooting and tuning documentation. The library itself is a C++ BitTorrent implementation, so the bindings are the practical entry point if you are not writing C++.

Language bindings listed on libtorrent.org

The site's navigation lists these bindings directly:

The site does not publish per-binding version numbers, supported libtorrent releases, or install commands in the material available here. Treat the binding pages themselves as the source for that detail, and check compatibility against the libtorrent version you plan to run.

Choosing between C++ and a binding

• Use the C++ library directly if you need the full interface and are building in C++. The site points to a tutorial as the introduction to using libtorrent in C++, plus the reference documentation.
• Use a binding if your project is in Python, Java, Go, or Node. The bindings are listed as first-class navigation items, which suggests they are maintained entry points rather than afterthoughts — but confirm the binding's own documentation for API coverage and build requirements.

Getting help and reporting problems

The site names three support routes:

1. Mailing list — described as the place for general libtorrent discussion and questions. An archive is linked.
2. IRC — #libtorrent on irc.freenode.net; the author is usually reachable there as hydri.
3. Bug tracker / GitHub — for reporting bugs; the project is hosted on GitHub, and patches can also be emailed to the mailing list or posted to the bug tracker.

For build or runtime problems, check the troubleshooting and tuning pages before posting — they are listed alongside the tutorial and reference in the documentation section.

What libtorrent is, in one paragraph

libtorrent is a feature-complete C++ BitTorrent implementation focused on efficiency and scalability. It is designed to run on embedded devices as well as desktops, and its stated goals are to be CPU efficient, memory efficient, and easy to use. It ships with a simple BitTorrent client that demonstrates the library's use.

License terms you should know before integrating

libtorrent is released under the BSD license. You can use it in your project without releasing your source code. The one requirement stated on the site: credit the author by including the libtorrent license in your software or documentation. Contributing features back is appreciated but not required; patches go to the mailing list or bug tracker.

Practical checklist

• Pick your language: C++ (tutorial + reference) or one of the four listed bindings.
• Read the troubleshooting and tuning pages if you hit performance or connectivity issues.
• Ask usage questions on the mailing list; report reproducible defects on the bug tracker or GitHub.
• Include the libtorrent license text in your product or docs to satisfy the BSD terms.

libtorrent is a feature-complete BitTorrent protocol implementation written as a C++ library. It is designed for efficiency and scalability, runs on embedded devices as well as desktops, and ships with a simple BitTorrent client that demonstrates how to use the library. It fits projects that need BitTorrent functionality embedded in a C++ application rather than a standalone client, and it is released under the BSD license, so you can use it in your project without releasing your source code as long as you include the libtorrent license in your software or documentation.

What the library actually provides

The project describes itself as a "feature complete C++ bittorrent implementation" with three stated main goals:

• CPU efficiency — keep processing overhead low.
• Memory efficiency — keep the footprint small enough for constrained hardware.
• Ease of use — a well-documented library interface intended to be straightforward to integrate.

Because it targets both embedded devices and desktops, the same library can serve a small appliance and a full desktop application. The bundled simple client is the practical starting point: it shows the library in use rather than only describing the API.

Where to start

The site organizes its material around a few entry points:

If you are evaluating the library, read the tutorial first and then check the upgrade guide for the version you plan to use — the existence of separate 2.1, 2.0, and 1.2 upgrade pages means API changes between major versions are documented and worth reviewing before you commit to a version.

Beyond the core protocol

The project lists a set of extensions and bindings that matter if your requirements go past basic torrent transfer:

• Transport and discovery: uTP extensions, DHT extensions (including DHT security and DHT store extensions), UDP tracker protocol, HTTP seed, and multi-tracker support.
• Streaming: a streaming extension and libtorrent plugins.
• Language bindings: Python, Java, Go, and Node, for teams that do not want to work in C++ directly.

For example, if you need a Python service that downloads and seeds torrents, the Python bindings are the relevant entry point; if you need to serve media while downloading, look at the streaming material.

License and support

libtorrent is BSD-licensed. The only requirement stated is that you credit the author by including the libtorrent license in your software or documentation; contributing features back is appreciated but not required. Patches can go to the mailing list or the bug tracker.

Support channels are the mailing list (with an archive) for general discussion, the bug tracker on GitHub for defects, and IRC. The site also notes a 2020 security audit, which is useful context if security review is part of your evaluation.

When it is a good fit — and when it is not

Choose libtorrent if you are building a C++ application (or using one of the available bindings) that needs a complete BitTorrent implementation and you care about CPU and memory cost on hardware ranging from embedded to desktop. The BSD license also makes it viable for closed-source products.

Look elsewhere if you want a ready-made end-user BitTorrent client rather than a library to integrate — the included client is described as simple and is there to demonstrate library use, not to compete as a full application. Also check the upgrade guides against your target version before starting, since the documented 1.2, 2.0, and 2.1 transitions indicate interface changes across releases.

Start with the official tutorial, which the project describes as an introduction to using libtorrent in C++. From there, use the reference documentation for API details, follow the site's download and building pages to get the library compiled, and study the bundled simple BitTorrent client as a working example of the library in use. libtorrent is a feature-complete C++ BitTorrent implementation focused on CPU efficiency, memory efficiency, and ease of use, and it runs on embedded devices as well as desktops.

A practical starting sequence

1. Read the tutorial first

The tutorial is the intended entry point for C++ users. It introduces how the library is used before you dive into the full API surface. Read it end to end once; it gives you the vocabulary (sessions, torrent handles, alerts) you will need when reading the reference.

2. Get and build the library

The site provides dedicated download and building pages. Use them rather than guessing at build steps, since libtorrent is a C++ library you compile and link into your own project. The building page is the authoritative source for prerequisites and build options.

3. Keep the reference documentation open

The reference documentation is where you look up exact class and function behavior. Use it as a lookup resource while writing code, not as a first read.

4. Study the bundled example client

libtorrent ships with a simple BitTorrent client that demonstrates use of the library. Reading its source is the fastest way to see how the pieces fit together in a real program. Compare what it does against the tutorial as you go.

What to expect from the library

The project also states it is a feature-complete BitTorrent protocol implementation, so you are not assembling partial protocol support yourself.

Licensing before you commit

libtorrent is released under the BSD license. You can use the library in your project without releasing your source code. The one requirement stated is that you credit the author by including the libtorrent license in your software or documentation. Contributing features back is appreciated but not required; patches can go to the mailing list or the bug tracker.

Where to get help

• Mailing list — the stated place for general libtorrent discussion and questions.
• Bug tracker / GitHub — for reporting bugs; the project is hosted on GitHub.
• IRC — the maintainer is usually reachable as hydri in #libtorrent on irc.freenode.net, per the site.

Common sticking points

• Skipping the tutorial and going straight to the reference. The reference documents the API but does not teach the flow; the tutorial does.
• Ignoring the example client. It is the clearest demonstration of library usage the project provides, so treat it as required reading rather than optional.
• Forgetting the license notice. BSD still requires the license text in your software or documentation, even though your source can stay closed.
• Version drift. The site lists upgrade guides for 2.1, 2.0, and 1.2, so check which version you are building against and read the matching upgrade notes if you follow older examples.

If you are evaluating whether libtorrent fits your project at all, the introduction and features pages give the project's own summary of scope and goals before you invest time in the tutorial.

libtorrent is a feature-complete C++ BitTorrent implementation that covers the core protocol plus a set of extensions for transport, discovery, seeding, and streaming. It is designed for CPU and memory efficiency and runs on embedded devices as well as desktops. If you need a BitTorrent engine you can embed in a C++ application, it is a strong candidate; if you need bindings for other languages, Python, Java, Go, and Node bindings are listed on the site.

Core protocol and transport

The site describes libtorrent as a complete BitTorrent protocol implementation and lists uTP among its extensions. uTP is the UDP-based transport that libtorrent uses alongside TCP, which matters when you want NAT-friendly, congestion-controlled transfers rather than plain TCP connections.

Discovery and tracker support

The extension list includes:

• DHT extensions — the mainline DHT plus additional DHT behaviors
• DHT security extension — hardened DHT participation
• DHT store extension — storing arbitrary data in the DHT
• UDP tracker protocol — tracker communication over UDP
• Multi-tracker — working with multiple trackers for one torrent

These are the pieces you evaluate when your application must find peers without relying on a single central tracker.

Seeding, streaming, and plugins

• HTTP seed — seeding or downloading via an HTTP source
• Streaming — treating torrent data as a stream rather than a whole-file download
• libtorrent plugins — extending behavior through the plugin interface

Streaming is the relevant feature if you want to start playback or processing before a download completes; plugins are relevant if you need custom peer or transfer logic without forking the library.

Choosing it: conditions that matter

The BSD license is the deciding factor for many commercial projects: the site states you do not have to release your source code, only credit the author by including the license. Contributions back are appreciated but not required.

Practical next steps

Start with the tutorial for a C++ introduction, then use the reference documentation for the specific extension you need. The site also provides a simple BitTorrent client as a working example of the library in use. For questions, the project points to its mailing list and IRC channel; bugs go to the GitHub issue tracker.